code: def test_expression():
      import mahotas as mh
      import numpy as np
  
      im = np.zeros((12, 16)) + np.arange(16)
      im -= im.mean()
      c0, c1 = 4, 7
      p0, p1 = 2, 3
      for p0, p1 in [(0, 1), (1, 0), (1, 2), (3, 2), (2, 0)]:
          sum_r = sum(
              (im[i, j] * (i - c0) ** p0 * (j - c1) ** p1)
              for i in range(im.shape[0])
              for j in range(im.shape[1])
          )
          mm_r = mh.moments(im, p0, p1, cm=(c0, c1))
          assert np.abs(mm_r - sum_r) < 1.0
  
file_path: mahotas/mahotas/tests/test_moments.py
imports: import numpy
  import mahotas
  from mahotas.features.moments import moments
  import pytest
label_desc: Use image node_id 6 for calling a global function with example usage: test_expression() without return types